644505447 has 4 divisors (see below), whose sum is σ = 859340600. Its totient is φ = 429670296.

The previous prime is 644505427. The next prime is 644505481. The reversal of 644505447 is 744505446.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 644505447 - 2⁶ = 644505383 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (644505427) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107417572 + ... + 107417577.

It is an arithmetic number, because the mean of its divisors is an integer number (214835150).

Almost surely, 2^644505447 is an apocalyptic number.

644505447 is a deficient number, since it is larger than the sum of its proper divisors (214835153).

644505447 is a wasteful number, since it uses less digits than its factorization.

644505447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214835152.

The product of its (nonzero) digits is 268800, while the sum is 39.

The square root of 644505447 is about 25387.1118286425. Note that the first 3 decimals coincide. The cubic root of 644505447 is about 863.7913765090.

Subtracting 644505447 from its reverse (744505446), we obtain a palindrome (99999999).

The spelling of 644505447 in words is "six hundred forty-four million, five hundred five thousand, four hundred forty-seven".